SPECTROSCOPIC INVESTIGATIONS OF SYNTHETIC BETA-AMYLOID PEPTIDES OF ALZHEIMERS-DISEASE

The chemical mechanism of binding between Congo red dye and amyloid pr oteins was investigated using infrared spectroscopy. Synthetic amyloid corresponding to the amino-acid residues 1 to 28 of Alzheimer's beta amyloid and insulin fibers prepared with the Burke and Rougvie method were used as substrates. Both peptides clearly demonstrate beta-pleate d sheet conformations. The analysis shows that Congo red binds to amyl oid proteins via interactions between the two negatively-charged sulfo nic acid groups of Congo red and two positively charged amino acid res idues of amyloid protein molecules. Evidence leads to the conclusion t hat the beta-pleated sheet conformation of the protein aids in orienti ng the dye molecules, thus favoring stabilisation and bonding.